"There is a very clear signal from the scientific community that we need to act on this issue," said de Boer.

"We have to turn the trend of global emissions in the next 10 to 15 years."

Global warming

The Kyoto pact, signed a decade ago, required industrial nations to reduce carbon dioxide and other heat-trapping gasses emitted by power plants and other industrial, agricultural and transportation sources.

Only 36 nations signed up to the pact, with the US and China, the world's biggest greenhouse gas emitters, remaining outside.

But prospects for a global deal were boosted recently when Kevin Rudd, whose party swept to power in Australia one week ago, immediately put signing the Kyoto pact at the top of his international agenda.

Australia had previously refused to sign the agreement.

George Bush, the US president who opposed Kyoto as a threat to US economic growth, also recently suggested the US would take part beyond 2012.

"We'd like to see consensus on the launch of negotiations. We want to see a Bali roadmap," said Paula Dobriansky, US undersecretary of state for democracy and global affairs.

Senior Beijing officials were reported by the Reuters news agency last week as saying that China would do more to strengthen its existing domestic targets to improve energy efficiency and curb greenhouse gas emissions, if other world powers shared relevant technologies.

"If help is forthcoming, if international cooperation is as it should be ... we will definitely do more," Yu Qingtai, a climate change negotiator, was quoted as saying.

Delegates at the Bali conference will also consider whether cuts in carbon emissions should be mandatory or voluntary, how to reduce deforestation, and ways to help poor countries expected to be hardest hit by worsening droughts, floods and violent storms.